1. Field of Invention
This invention pertains to a method for fabricating a detector array for use in imaging applications such as X-ray imaging, fluoroscopy, positron emission tomography (PET), single photon emission computed tomography (SPECT), computed tomography (CT), gamma camera and digital mammography systems. More particularly, the present invention provides a simple approach for fabricating a detector array with high packing fraction resulting in greater sensitivity while still maintaining spatial resolution.
2. Description of the Related Art
In the field of imaging, it is well known that imaging devices incorporate a plurality of scintillator arrays for detecting radioactivity from various sources. It is also common practice, when constructing scintillator arrays composed of discrete scintillator elements, to pack the scintillator elements together with a reflective medium interposed between the individual elements fully covering at least four sides of the scintillator element. The reflective medium serves to collimate the scintillation light to accurately assess the location at which the radiation impinges upon the detectors. The reflective medium further serves to increase the light collection efficiency from each scintillator element as well as to control the cross-talk, or light transfer, from one scintillator element to an adjacent element. Reflective mediums include reflective powders, reflective film, reflective paint, or a combination of materials.
Conventionally, scintillator arrays have been formed from polished crystals that are either hand-wrapped in reflective PTFE tape and bundled together, or alternatively, glued together using a white pigment such as BaSO4 or TiO2 mixed with an epoxy or RTV.
Another approach utilizes individual reflector pieces that are bonded to the sides of the scintillator element with the aid of a bonding agent. This process requires iterations of bonding and cutting until a desired array size is formed.
Other devices have been produced to form an array of scintillator elements. Typical of the art are those devices disclosed in the following U.S. Patents:
Patent No.Inventor(s)Issue Date3,936,645A. H. IversonFeb. 3, 19764,914,301Y. AkaiApr. 3, 19904,982,096H. Fujii et al.Jan. 1, 19915,059,800M. K. Cueman et al.Oct. 22, 19916,292,529S. Marcovici et al.Sep. 18, 2001
Of these patents, the '645 patent issued to Iverson discloses a radiation sensitive structure having an array of cells. The cells are formed by cutting narrow slots in a sheet of luminescent material. The slots are filled with a material opaque to either light or radiation or both. The '800 patent issued to Cueman et al., discloses a similar scintillator array wherein wider slots are formed on the bottom of the array.
Most of the aforementioned methods also require a separate light guide attached to the bottom of the detector array to channel and direct the light in a definitive pattern on to a receiver or set of receivers such as photomultiplier tubes or diodes. This light guide usually contains cuts in varying depths to alter the light pattern on the receivers. This additionally complicates the fabrication of the entire detector.
Wong, W. H. et al., in “An Elongated Position Sensitive Block Detector Design Using the PMT Quadrant-Sharing Configuration and Asymmetric Light Partition,” IEEE Transactions on Nuclear Science, Vol. 46, No. 3, 542–545 (1999), discloses a block design wherein seven (7) monolithic BGO slabs are painted with light-blocking reflective patterns on their boundaries. The slabs are then glued together to form a block. The block is then cut orthogonally with respect to the glued seams and painted and glued again in like fashion. A 7×7 array is thus defined. The reflective patterns are unclear from the disclosure, but appear to be defined such that the reflective areas increase toward the central portion of the array.